Cut the puckered ends off each tube of polenta, then cut into 12 slices, each about 1/2 inch thick. Heat a wide nonstick griddle that has been generously sprayed with olive oil cooking spray. Arrange the polenta slices on the griddle. Cook both sides over medium-high heat until golden and crisp, about 8 minutes per side.

Meanwhile, heat the olive oil in a wide skillet or steep-sided stir-fry pan. Add the garlic and sauté over low heat for a minute or so, until turning golden.

Add the beans, roasted pepper, and cumin. Stir together and cook over medium heat until well heated through.

Add the spinach, cover, and cook just until it wilts, 1 to 2 minutes. Stir the mixture together, season with pepper, and remove from the heat.

To serve, arrange 3 or 4 polenta slices on each plate and spoon the bean mixture evenly over each serving.